Reconfigure the Exchange/mail server
An attempt to send an E-mail notification fails with the following error:
response : 535 5.7.3 Authentication unsuccessful
The Exchange/mail server is configured incorrectly.
Solution for Exchange Server 2007/2010/2013/2016
Open Exchange System Manager:
Enable anonymous relaying for the Acronis Backup.
Solution for Exchange Server 2003
Create a new domain user / administrator
Use this account to send E-mail notifications: